JPH11201910A - Device for inspecting recessed part of laminated material and laser beam machining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a recessed part inspecting device capable of speedily and easily detecting the state of a residual material remaining at the bottom part of a machined hole part in a laminated material such as a printed board in non-destructive inspection. SOLUTION: The machined hole part 6 of a printed board 21 is formed by a laser beam 20 by removing an epoxy resin 18. If a bottom part 6a is plated as a residual resin 22 remains there, and a blind via hole is formed, a layer of plating is peeled off from a copper foil 24 due to the residual resin 22, and a conduction failure occurs. For preventing this, it is necessary to detect the presence or absence of the residual resin 22 at the bottom part 6a and remove it if necessary. When the copper foil 24 is irradiated with exciting light 7, the residual resin 22 is excited to emit luminescence 8. Fluorescence in the luminescence 8 is detected by a CCD camera 11, and a detected image is processed by an image processing device 12 to detect the presence or absence, etc., of the residual resin 22. As the residual resin 22 radiates fluorescence, it is possible to detect the presence or absence of the residual resin 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concave portion formed by irradiating a laminated material such as a so-called printed circuit board with a laser beam to form a blind via hole, a groove or the like. Inspection equipment for the concave portion of the laminated material for inspecting, in particular, the situation of the residual material remaining without being removed at the bottom of the concave portion can be known without performing a destructive inspection, and the thickness of the residual material can be known. The present invention relates to a laminated material concave portion inspection device capable of performing detection and the like, and a laser processing device provided with such a concave portion inspection device.

[0002]

2. Description of the Related Art With the recent increase in the performance of electronic equipment, higher density wiring is required. To satisfy this demand, a multilayer printed circuit board and a smaller printed circuit board are required. For that purpose, it is essential to form a fine perforation hole called a blind via hole (hereinafter referred to as BVH) having a hole diameter of about 150 μm for interlayer conductive connection. However, it is difficult to drill a hole having a diameter of 0.2 mm or less in the current drilling process.
Since it is difficult to control the depth with this accuracy, it is impossible to form a fine BVH by drilling.

As a BVH forming method replacing the drilling, a method using a laser beam such as a carbon dioxide gas laser, a YAG laser, an excimer laser, etc., has attracted attention and has been partially put to practical use. Among these processing methods, the processing method using a carbon dioxide laser utilizes the difference in the absorptivity of the light energy of the carbon dioxide laser with respect to a resin or glass fiber as an insulating base material constituting a printed circuit board and copper as a conductor layer. is there.

FIGS. 10 to 14 show a conventional BVH processing method for a printed circuit board. FIG. 10 is an explanatory view for explaining a step of processing a fine through-hole portion, and FIG. 11 is a concave portion for forming a BVH. It is explanatory drawing explaining the processing method which processes a part. FIG. 12 is a configuration diagram of a laser processing apparatus provided with an optical microscope, FIG. 13 is a configuration diagram of an optical microscope, and FIG. 14 is an explanatory diagram for explaining a state of reflection of irradiated light.

For example, since copper reflects most of a carbon dioxide gas laser, as shown in FIG.
The copper foil removing portion 36 is formed by etching or the like so as to form a hole of a required diameter in the copper foil 24 on the surface of the first surface, and the copper foil removing portion 36 is irradiated with a laser beam 20 which is a carbon dioxide gas laser. As shown in FIG. 1, the epoxy resin and the glass fiber constituting the printed circuit board 21 are selectively decomposed and removed.
A fine processing hole 37 penetrating the printed circuit board 21 can be formed as shown in FIG.

Further, as shown in FIG.
If the inner copper foil 24 is previously laminated inside the printed circuit board 1, the printed circuit board 21 can be disassembled / disassembled when the laser beam 20 is irradiated.
Since the removal stops at the inner layer copper foil 24, the inner layer copper foil 24
When the hole is securely stopped, the hole processing portion 6 (hereinafter simply referred to as the hole processing portion 6) can be formed. However, when stopping at the inner layer copper foil 24 in this way, when the hole processing portion 6 is processed with a carbon dioxide gas laser, even if the laser beam is sufficiently irradiated, the thickness is 1 μm.
The following insulating copper or resin is used as the inner layer of copper foil 2
4, that is, at the bottom 6 a of the hole processing portion 6.

Therefore, after laser processing, it is necessary to completely remove the residual resin by etching the residual resin with permanganic acid or the like. At this time, the hole diameter of the hole processing portion 6 is 100 μm.
When the diameter is reduced to about m, it becomes difficult for the etchant to reach the inside of the hole processing portion 6. For this reason, if the thickness of the residual resin is increased due to poor laser processing conditions or the like, the hole processing portion 6 is likely to occur if the residual resin cannot be completely removed by etching. When plating is performed in this state to form a BVH, some resin remains between the plating film and the inner copper foil 24.

Here, when stress is applied by a thermal cycle or the like, cracks are generated and propagate, and the plating film is peeled off. When the plating film is peeled off, the conduction between the inner copper foil 24 and the plating film becomes non-conductive, resulting in a product failure. Further, if the resin remains over the entire surface between the plating film and the inner layer copper foil 24, it becomes defective due to non-conduction from the beginning. For this reason, it is necessary to inspect the thickness of the residual resin after the laser processing, and when the thickness is large, further perform laser processing to remove the residual resin.

Further, there is a processing method using a YAG laser or an excimer laser. This processing method utilizes the fact that the removal depth per pulse is on the order of 1 μm. In these processing methods, since the removal amount of one pulse is small, the number of pulses required for processing increases, and the influence of disturbance such as energy fluctuation during processing is averaged. By taking advantage of this fact, the number of pulses is appropriately selected to uniformly form a drilled portion that stops near the inner copper foil 24.

[0010] However, when energy is changed over a long period of time even in a processing method using a YAG laser or an excimer laser, a resin having a thickness of 1 μm or less remains on the inner copper foil 24 like the carbon dioxide laser. In some cases.

For this reason, a conventional laser processing apparatus for a laminated material is equipped with an optical microscope as shown in FIG. However, Nikkei Science 199
In a conventional optical microscope as shown on page 45 of the October 2000 issue, 10 mm is formed at the bottom 6a of the hole processing portion 6 shown in FIG.
Although a processing defect in which the residual resin 22 of about μm or more remains can be detected, it is impossible to detect the residual resin 22 of about several μm as described above. The printed circuit board 21
Has an epoxy resin 18 and a glass epoxy 19, and a copper foil 24 is provided therebetween.

For this reason, under the present circumstances, after plating, the hole processing portion 6 is cut and polished by a destructive inspection, and then the residual resin thickness is inspected by cross-sectional observation, or the hole processing portion 6 for inspection is used instead of the destructive inspection. In the same way, after cutting and polishing the hole processing portion, the thickness of the residual resin was inspected by observing the cross section. Therefore, the time required for the inspection was significantly long. Even with this other method, it was not possible to easily detect the residual resin without destroying the substrate.

Hereinafter, the reason why the residual resin cannot be detected by the conventional optical microscope will be described. A conventional optical microscope is configured as shown in FIG. The white light 38 for illumination of the optical microscope emitted from the light source 1 is applied to the printed board 21 via the objective lens 5 by the beam splitter 25. The reflected light from the printed circuit board 21 forms an inverted real image 27 enlarged by the objective lens 5 in front of the imaging lens 9 (FIG. 1).
3 (to the right of 3) and this real image
It is detected by the camera 11.

Returning to FIG. 12, this image is
2 to determine the presence or absence of residual resin. This determination result is transmitted to the laser oscillator 13 and the control device 13 for controlling the processing table 17, and when the residual resin 22 is larger than a predetermined thickness, the laser beam 20 is positioned by moving the processing table 17, Transfer mask 1
4. The laser beam is again applied to the hole processing portion 6 of the printed circuit board 21 via the positioning mirror 15 and the transfer lens 16 to further remove the residual resin 22.

Here, as shown in FIG. 14, when white light 38, which is illumination light of an optical microscope, is irradiated on the surface of the residual resin 22, a part thereof is reflected as reflected light 29 from the surface.
Others reach the bottom copper foil 24 through the residual resin 22 and are almost reflected as reflected light 30. Accordingly, the white light 3 is applied to the thin residual resin 22 on the copper foil 24.
8 as illumination light, most of the reflected light is
4 is the reflected light 30 returning from the
2 is not visible.

[0016]

The optical microscope, which is a conventional device for inspecting a recessed portion of a laminated material, is configured as described above, and has a problem that detection cannot be performed when the residual resin is thin. The present invention has been made in order to solve the above-mentioned problems, and it is possible to easily know the state of the material remaining without being removed at the bottom of the concave portion of the laminated material easily and nondestructively. It is another object of the present invention to obtain a concave portion inspection device capable of detecting the thickness of the remaining material and a laser processing device including such a concave portion inspection device.

[0017]

In order to achieve the above-mentioned object, in the apparatus for inspecting a concave portion of a laminated material according to the present invention, a first material and a second material are processed into a laminated material formed in layers. Irradiating a laser beam with a laser beam irradiating device for irradiating a residual material, which is the first material remaining without being removed at the bottom of the recess formed by removing the first material, An illumination light irradiation device is provided.
By irradiating the residual material with illumination light, it is possible to reliably know the state of the residual material based on the light from the residual material.

Further, a light detection device for detecting light from the residual material irradiated with the irradiation light is provided. Provision of the light detection device enables mechanization of detection.

Further, the illumination light irradiating device irradiates an excitation light for exciting the residual material to emit luminescence. The residual material is irradiated with excitation light to emit luminescence, and the status of the residual material can be surely known without performing a destructive inspection by visually observing the luminescence or measuring with a device.

Further, the illumination light irradiating device is configured to irradiate excitation light for exciting the residual material to emit luminescence, and the light detecting device is configured to detect luminescence emitted from the residual material. As described above, the state of the residual material can be known by detecting the luminescence by the light detection device.

The illumination light irradiating device irradiates ultraviolet light having an absorption coefficient of a predetermined value or more with respect to a residual material, and the light detecting device detects reflected light reflected from the bottom of the concave portion. . Since ultraviolet light is absorbed while passing through the residual material, the greater the thickness and the absorption coefficient of the residual material, the greater the rate of reduction. Therefore, in order to know the state of the residual material with high sensitivity, it is preferable to secure the sensitivity to the thickness by using ultraviolet light having an absorption coefficient equal to or more than a predetermined value.

Further, an ultraviolet light irradiator is used, and the absorption coefficient is 5
Irradiation of ultraviolet light of 000 / cm or more was performed. When an ultraviolet light having an absorption coefficient of 5000 / cm or more is used, the reflected light intensity is reduced by about 20% when the thickness of the residual material is 0.6 μm as compared with the case where the thickness of the residual material is 0.2 μm. %Change. If it changes to this extent, it can be easily detected by the reflected light detection device. The thickness of the residual material is 0.
If it is about 2 μm, it can be removed by the chemical treatment, so that no defect occurs. If it exceeds about 0.6 μm, it cannot be removed by the chemical treatment, and it often becomes defective. Therefore, this difference can be easily detected.

Also, the illumination light irradiating device may include a first irradiation light whose absorption coefficient for the residual material is a first predetermined value and a second predetermined value whose absorption coefficient for the residual material is smaller than the first predetermined value. And irradiate the second irradiation light, and the light detection device detects the thickness of the residual material based on each reflected light of the first and second irradiation lights reflected from the bottom of the concave portion. To do. The absorption coefficients of the first and second irradiation lights with respect to the residual material are made different, and those reflected on the surface of the residual material occupy a majority of the first reflected light, and those reflected on the surface of the second material are By occupying the majority of the second reflected light, the position of the surface of the residual material and the position of the surface of the second material can be detected from the first and second reflected light, and the residual material can be detected from the difference between the positions of the two surfaces. You can know the thickness of the.

Then, the laser beam of the processing laser beam irradiation device is used as the illumination light irradiation device. A laser beam irradiation device for processing is used as the illumination light irradiation device to reduce the cost of the device.

Further, the laser processing apparatus according to the present invention is provided with one of the above-described concave portion inspection devices for the laminated materials. With such a laminated material concave portion inspection device, it is possible to immediately know the state of the residual material without performing a destructive inspection after processing the concave portion, and if necessary, a process of removing the residual material again. It can be performed.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 show an embodiment of the present invention, and FIG. 1 shows a configuration of a laser processing apparatus provided with a recessed portion inspection device (hereinafter sometimes simply referred to as an inspection device). FIGS. 2A and 2B are explanatory diagrams for explaining the reflected light intensity when there is a residual resin in the recessed portion and when there is no residual resin.

In FIG. 1, a printed circuit board 21 which is a laminated material has an epoxy resin 18 and a glass epoxy 19 formed in layers. The laser processing apparatus uses a carbon dioxide laser as the laser oscillator 13. The processing laser beam 20 emitted from the laser oscillator 13 is applied to the printed board 21 via the transfer mask 14, the positioning mirror 15, and the transfer lens 16, and the epoxy resin 18 is removed to form a hole having a predetermined diameter. The hole processing part 6 is formed. At this time, even though the laser beam 20 is applied as described above, the residual resin 2
2 may remain.

In this embodiment, a mercury lamp is used as the light source 1 for generating ultraviolet light for exciting the residual resin as illumination light. The excitation filter 3 mainly transmits the excitation light 7, which is ultraviolet light having a wavelength near the wavelength at which the residual resin 22 is excited, and has a transmission characteristic around 330 to 380 nm. Dichroic mirror 4 is 38
A material having a characteristic of reflecting light at 0 nm or less and transmitting light at 400 nm or more is used. The absorption filter 10 has 41
A filter that absorbs a wavelength of 0 nm or less was used.

The light emitted from the light source 1 passes through the excitation filter 3, the dichroic mirror 4, and the objective lens 5, and is applied to the bottom 6a of the processed hole processing portion 6. The excitation light 7 that has passed through the excitation filter 3 has a wavelength range in which the residual resin 22 at the bottom 6a of the hole processing portion 6 is excited to generate fluorescence. Occur. The luminescence 8 forms an image on the CCD camera 11 through the absorption filter 10 that mainly transmits a wavelength near the fluorescence wavelength by the objective lens 5 and the imaging lens 9. This image is analyzed by the image processing device 12 to determine the presence or absence of the residual resin 22.

The result of this determination is transmitted to the laser oscillator 13 and a controller 23 for controlling the processing table 17. If the thickness of the residual resin 22 is larger than a predetermined thickness, the processing table 17 is moved to The laser beam is again radiated to the hole processing portion 6 to further remove the residual resin 22.

In the present embodiment, as described above, a carbon dioxide laser is used as the laser oscillator 13, a mercury lamp is used as the light source 1 for generating the excitation light 7, and a copper foil on the bottom 6 a of the drilled portion 6 is used as a test sample. A hole processing portion 6 in which a residual resin 22 of an epoxy resin having a thickness of 1 μm or less partially remains on
The printed circuit board 21 in which the epoxy resin was completely removed and the hole processing portion 6 where the residual resin did not remain on the copper foil 24 was observed by the CCD camera 11.

As a result of observing the above sample, the epoxy resin 2
The drilled portion 6 where 2 remained remained bright, and the drilled portion 6 where the copper foil 24 was exposed provided a dark image, and the residual resin 22 could be easily identified by visual observation of the brightness of the image. . Note that the observation may be performed without directly using the CCD camera 11 by directly observing the fluorescence from the residual material.

Further, as shown in FIG. 2, the image processing device 12 converts the circular image 33 of the drilled portion into an average X of the reflected light intensities x in a predetermined rectangular area 34 as shown in FIG. When the light intensity is higher than the reflected light intensity 35, a hole-processed portion where the residual resin remains more than a predetermined thickness. When the average Y of the reflected light intensity y is lower than the reflected light intensity 35, the hole-processed portion where the epoxy remains less than the predetermined thickness. As a result of discriminating the drilled portion, it was possible to easily determine the drilled portion where the epoxy remained more than a predetermined thickness. This determination was performed by the image processing device 12. It should be noted that the determination can be made visually without using a machine.

As Comparative Example 1, the printed circuit board 21 of this sample was plated, the section was polished, and the presence or absence of residual resin between the plating layer and the copper foil was observed with an electron microscope. Comparing this observation result with the result determined by the image processing device 12 described in the present embodiment based on the brightness of the drilled portion,
Both results corresponded well, and the validity of this inspection device was verified.

As a comparative example 2, the excitation filter 3 and the dichroic mirror were used as the illumination light in the first embodiment as visible light without exciting the residual resin 22 of the epoxy resin in order to compare with the conventional method. When the same test was performed except for No. 4, no shading occurred between the drilled portions, and it was not possible to detect the amount of the residual resin or the presence or absence of the residual resin.

As described above, according to the present invention, the residual resin 24 on the copper foil 24 can be easily detected without destruction. Note that the residual resin 22 is not limited to the epoxy resin,
A polyimide resin or another resin may be used, and the fluorescent light is similarly emitted by irradiating excitation light having an appropriate wavelength in accordance with the type of the resin, so that it can be easily determined.

The CCD camera 11 is intended for visible light. In order to visually protect the eyes when determining the brightness of the hole processing portion 6, the CCD camera 11 is provided with an absorption filter 10 that mainly transmits only the fluorescence wavelength. Although used, the absorption filter 10 is not indispensable. For example, when a photodiode or the like is used, it is unnecessary because luminescence including ultraviolet rays can be detected.

Embodiment 2 FIG. 3 is a configuration diagram of an inspection apparatus and a laser processing apparatus according to another embodiment of the present invention. In FIG. 3, the wavelength 473 is used as the laser oscillator 13.
nm second harmonic of a YAG laser is used. The laser oscillator 13 is a laser beam 20 for processing the hole processing portion 6.
(See FIG. 1) and the bottom 6a of the drilled portion 6
The excitation light 7 for exciting the residual resin 22 of the epoxy resin remaining on the substrate is generated. Specifically, the laser oscillator 13
The light source 1 shown in FIG.
Used as equivalent to

When forming the hole processing portion 6, the laser beam output from the laser oscillator 13 passes through the objective lens 5 by the dichroic mirror 4, and
1 to form a drilled portion 6. Thereafter, the output is squeezed to the bottom 6a of the processed hole 6 to about 10% as excitation light 7. By setting the excitation laser beam to a wavelength range in which the residual resin 22 in the hole processing portion 6 is excited to generate fluorescence, the luminescence 8 is generated when the residual resin 22 exists. The dichroic mirror 4
The filter has a characteristic of reflecting light at 490 nm or less and transmitting light at 505 nm or more, and the absorption filter 10 uses a filter absorbing a wavelength of 520 nm or less.

The luminescence 8 forms an image on a CCD camera 11 through an absorption filter 10 that transmits only a wavelength near a fluorescence wavelength by an objective lens 5 and an imaging lens 9. The brightness of the image is analyzed by the image processing device 12, and the presence or absence of the residual resin 22 and the degree of the residual resin 22 are determined. This determination result is transmitted to the control device 23 which controls the laser oscillator 13 and the processing table 17, and when the residual resin 22 is larger than a predetermined thickness, the laser intensity is increased and the laser beam is again irradiated to the hole processing portion 6 again. Then, the residual resin 22 is further removed.

In the present embodiment, the second harmonic of the YAG laser having a wavelength of 473 nm is used as the laser oscillator 13 as described above. As a test sample, a hole processing part 6 in which an epoxy resin having a thickness of 1 μm or less partially remained on a copper foil 24 and a hole processing part 6 in which the epoxy resin was completely removed and no epoxy resin remained remained mixed. Using the printed circuit board 21,
The bottom 6a of the drilled portion 6 was observed. As a result of observing the test sample, the drilled portion 6 where the epoxy resin remains on the bottom 6a is bright, and the drilled portion 6 where the copper foil is exposed gives a dark image, and the residual resin 22 is clearly shown. Could be detected.

As shown in FIG. 2, when the average of the reflected light intensity in the predetermined area is brighter than the predetermined reflected light intensity, the epoxy is larger than the predetermined thickness. The remaining hole processing part, if dark, it is determined that the hole processing part where the residual epoxy is less than the predetermined thickness,
As a result of determining the presence / absence and degree of the residual resin in the hole processing portion 6, it was possible to easily determine the hole processing portion where the epoxy remained more than a predetermined thickness.

After plating the printed circuit board of this sample, the cross section was polished and observed with an electron microscope, and the state of the residual resin between the plating layer and the copper foil was observed. When this result was compared with the determination result by the inspection device described in the present embodiment, both results corresponded well, and the validity of the determination by the inspection device was verified.

Embodiment 3 FIG. 4 to 7 show still another embodiment of the present invention. FIG. 4 is a configuration diagram of an inspection device and a laser processing device, and FIG. 5 is an explanatory diagram for explaining a state of reflection. FIG. 7 is a characteristic diagram showing the relationship between the residual film pressure of the residual material and the intensity of the reflected light, and FIG. 8 is an explanatory diagram for explaining the intensity of the reflected light with and without the residual resin in the recessed portion.

In these figures, a light source 1 emits ultraviolet light 2 for illumination, and irradiates a printed circuit board 21 from a beam splitter 25 via an objective lens 5. The reflected light 32 from the bottom of the hole processing portion of the printed circuit board 21 (not shown in FIG. 4) is transmitted through the objective lens 5 and the imaging lens 9 to pass only a wavelength near the ultraviolet light 2 for illumination. An image 27 is formed on the image intensifier 26 mounted on the CCD camera 11 via the filter 31.

The image 27 is analyzed by the image processing device 12, the analysis result is displayed on the CRT 28, and the analysis result is sent to the control device 23. Here, the image intensifier 26 is a device that can increase the intensity of incident light by tens of thousands of times. By adjusting the voltage applied to the image intensifier 26, the gain can be adjusted and the degree of enhancement of the incident light intensity can be reduced. It is possible to change.

By the way, as shown in FIG. 5, when the ultraviolet light 2 for illumination is applied to the surface of the residual resin 22 remaining at the bottom of the hole processing portion of the printed circuit board 21, a part of the resin surface is reflected from the surface. Reflected as light 29 and objective lens 5 (FIG. 4)
The others reach the copper foil 24 at the bottom of the drilled portion through the residual resin 22 while being absorbed by the residual resin 22.

The ultraviolet light 2 that has reached the copper foil 24 is partially absorbed and the rest is reflected as the copper foil surface reflected light 30 and passes through the residual resin 22 while being absorbed again.
2 and reaches the objective lens 5. Copper foil surface reflected light 30
Is significantly larger than the resin surface reflected light 29, it becomes difficult to detect the resin surface reflected light 29,
The resin surface cannot be detected. That is, the residual resin 22 cannot be detected, and only the copper foil 24 can be detected.

Therefore, in order to detect the residual resin 22, it is necessary to use light in which the residual resin reflected light 29 on the surface of the residual resin 22 is larger than the copper foil reflected light 30 on the surface of the copper foil 24. is there. Therefore, in this embodiment, the copper foil 2
Ultraviolet light (reflectance: about 30%) having a low reflectance for No. 4 was used as illumination light. The visible light has a reflectance of about 70 to 95% with respect to the copper foil 24, and 30% of the ultraviolet light.
Much higher than.

Now, the absorption coefficient for the residual resin is α / cm
It is assumed that the ultraviolet light 2 having the intensity K is incident on the residual resin 22. The absorption coefficient of the residual resin 22 for the ultraviolet light 2 is α / c
m, the intensity J (z) of the ultraviolet light at a depth z from the surface of the residual resin 22 is expressed by J (z) = Kexp (-αz) (1)

Assuming that the reflectance of the surface of the residual resin 22 with respect to the ultraviolet light 2 is about 10%, the intensity A of the resin surface reflected light 29 is as follows. A = 0.1K (2) Further, the intensity B of the incident light incident on the residual resin 22 is B = 0.9K (3). Accordingly, the intensity C of the ultraviolet light 2 that has passed through the residual resin 22 having a thickness of d (cm) while attenuating and has reached the surface of the copper foil 24 is: C = 0.9 K · exp (−α · d) (4) ).

The intensity D of the copper foil surface reflection light 30 on the surface of the copper foil 24 is such that the reflectance on the surface of the copper foil 24 is 30%.
It is as follows. D = 0.9K · {exp (−α · d)} · 0.3 (5) The reflected light further passes through the residual resin 22 while attenuating, and from the surface of the residual resin 22 to the copper foil surface Reflected light 3
It goes out with 0. The intensity E of the copper foil surface reflected light 30 is further attenuated by exp (−α · d) in the residual resin 22 having the thickness d from the value of the above equation (5), and E = 0.9 K · ｛exp (−2α · d)｝ · 0.3 (6)

The reflected light intensity R from the bottom of the drilled portion is the sum of the copper foil surface reflected light 30 and the resin surface reflected light 29 from the copper foil 24, so that R = A + E (7). FIG. 6 shows the relationship between the residual film thickness t of the residual resin and the reflected light intensity R for some absorption coefficients α. The greater the slope of this curve, the more the brightness at the bottom of the drilled portion changes with the change in the residual film thickness.

If the residual film thickness is about 0.2 μm, it can be removed by a chemical treatment, so that no defect occurs. If it exceeds about 0.6 μm, it cannot be removed by the chemical treatment, resulting in many cases of failure. In order to detect the change in the reflected light intensity due to the difference in the film thickness by a machine, for example, to detect the change in the reflected light intensity R by about 20% or more, the CCD camera 11 and the image processing device 12 need to detect the change. That is, the residual film thickness is 0.2 μm
In order for the difference between the reflected light intensity in the case of (1) and the reflected light intensity in the case of the residual film thickness of 0.6 μm to be 0.2 (20%), it is necessary to use FIG.
More necessary is an absorption coefficient α ≧ 5000 / cm. According to FIG. 6, when the absorption coefficient α = 5000 / cm, the reflected light intensity at the residual film thickness of 0.2 μm is about 0.32,
The reflected light intensity when the residual film thickness is 0.6 μm is about 0.25, and 0.25 / 0.32 = 0.78, which means that there is a change of more than 20%.

Based on the above examination, in the present embodiment,
A nitrogen laser that generates ultraviolet light 2 having a wavelength of 337 nm was used as a light source 1 that generates illumination light, and a polyimide resin having a thickness of about 1 μm and a thickness of about 0.4 μm remained on a copper foil 24 as a sample printed circuit board 21. A printed circuit board with a mixture of holes was used. Note that the wavelength 337 used in this embodiment is used.
The absorption coefficient of UV light of 10 nm to polyimide resin is about 8
000 / cm. Further, a filter having a band pass width of 10 nm around 337 nm was used as the band pass filter 31.

As a result of inspecting the printed circuit board 21 using the inspection apparatus of the present embodiment, by adjusting the gain of the image intensifier 26, the hole processing portion where the polyimide remains about 1 μm is dark, and A bright image was obtained in the hole processed portion where 0.4 μm remained.

As shown in FIG. 7, when the average U of the intensity of the reflected light u in the predetermined area 34 is higher than the predetermined intensity 35 of the reflected light, as shown in FIG. It is determined that the hole is a hole processed portion where the polyimide remains about 0.4 μm, and when the average V of the intensity of the reflected light v is darker than the intensity level 35 of the reflected light, it is determined that the polyimide is a hole processed portion where the polyimide remains about 1 μm. , As a result of discriminating the hole machining part,
The drilled portion where 1 μm of the polyimide remained could be easily identified. This determination was performed by the image processing device 12 that analyzes the image of the intensifier 26.

After plating the printed circuit board, the cross section was polished and observed with an electron microscope. As a result, a residual resin portion was observed between the plating layer and the copper foil. When the observation results were compared with the results of the inspection device described in the present embodiment, both results corresponded to 100%, and the validity of the detection by the inspection device was verified.

As a comparative example 1, the same test was performed except that the band-pass filter 31 was used with the light source 1 shown in FIG. Even if the gain was adjusted, the brightness of the bottom portion of the drilled portion did not change because the residual resin 22 was thick and thin, and the magnitude of the residual resin thickness could not be detected.

Further, as Comparative Example 2, a band-pass filter using a He-Cd laser which generates light at a wavelength of 442 nm having an absorption coefficient for polyimide of about 4000 / cm without using a nitrogen laser in this embodiment was used. When the same test was performed with this wavelength changed, the discrimination was successful, but the coincidence rate with the cross-sectional observation result was 80%.
%. That is, the absorption coefficient is about 4000
/ Cm lowers the accuracy of the discrimination.

In the case of a resin other than polyimide, light having a wavelength such that the absorption coefficient becomes 5000 / cm or more may be selected according to the resin. As described above, according to the present invention, the residual thickness of the residual resin 22 on the copper foil 24 can be easily detected nondestructively.

Embodiment 4 8 and 9 show still another embodiment of the present invention. FIG. 8 is an explanatory diagram for explaining the operation of the inspection device and the laser processing device.
FIG. 3 is an explanatory diagram for explaining a light path when the focal position is shifted. In FIG. 8, a light source 1 can be generated by switching between ultraviolet light 2 (FIG. 8A) and white light 38 (FIG. 8B) as illumination light. First, in the case of the ultraviolet light 2, as shown in FIG. 8A, the ultraviolet light 2 emitted from the pinhole plate 39a placed in front of the light source 1 passes through the objective lens 5 by the beam splitter 25 and passes through the residual resin. Irradiation is performed on the surface 22. At this time, when the printed circuit board 21 is set so as to be focused on the residual resin 22, the reflected light 32 a from the surface of the residual resin 22 is reflected by the objective lens 5.
The focus is on the position of the pinhole plate 39b provided in front of the photodetector 40, and the light passes through the pinhole plate 39b and is detected by the photoelectric detector 40.

In the optical system using the ultraviolet light 2, the point light source generated by the pinhole plate 39 a on the light source 1 side and the photoelectric detector 4
The pinhole plate 39b on the 0 side has a conjugate positional relationship with the objective lens 5. Such an optical system is called a confocal optical system. In the case of the confocal optical system, if the focus is shifted on the residual resin 22 as the sample as shown in FIG. 9, the reflected light 32a is largely blurred before the pinhole plate 39b on the photoelectric detector 40 side, and It cannot pass through the plate 39b.

As described above, the photoelectric detector 40 has the residual resin 2
Since the reflected light 32a can be detected only when the focus is on the focal point 2, the focal position can be accurately detected. The adjustment of the focal position is performed on the processing table 17 on which the printed circuit board 21 is placed.
(See FIG. 1) in the left-right direction of FIG.

Here, the reflected light 32a of the ultraviolet light 2 is shown in FIG.
As shown in the figure, the resin surface reflected light 29 and the copper foil surface reflected light 30
There are two types. In order to detect at least the resin surface with ultraviolet light, the intensity A of the resin surface reflected light 29 is only 10% of the incident intensity. And must be.
Therefore, in order to satisfy A ≧ E in the equations (2) and (6) described in the third embodiment, the absorption coefficient α ≧ 5000 / cm is required with the residual resin thickness d being 1 μm. Becomes

Next, in order to find the position of the copper foil 24, the illumination light is switched to the white light 38 and the focus position is detected. At this time, the white light 38 has a significantly lower absorption coefficient for the residual resin 22 and a higher reflectance for the copper foil 24 than the ultraviolet light 2, so that the intensity of the copper foil surface reflected light 30 of the copper foil 24 is higher.
Therefore, the position of the copper foil 24 can be accurately detected by detecting the focal position of the surface of the copper foil 24 in accordance with the principle of FIG. The focal position can be adjusted in the same manner as in the case of the ultraviolet light 2 by using the processing table 17 on which the printed circuit board 21 is mounted.
(See FIG. 1) in the left-right direction of FIG.

As a result, the difference d (FIG. 8B) between the focal positions of the ultraviolet light 2 and the white light 38 becomes the residual film thickness, and the residual film thickness can be easily measured nondestructively. Then, when the residual film thickness is equal to or more than a predetermined value, for example, 0.15 μm or more, the processing laser beam is again irradiated to the hole processing portion 6 to remove the residual resin.

Based on the above examination, in the present embodiment, a nitrogen laser having a wavelength of 337 nm
A halogen lamp light was used as a printed circuit board 21, and a printed circuit board 21 having a hole processed portion 6 in which a polyimide resin having a thickness of about 1 μm remained as a residual resin 22 on a copper foil 24 was used. Note that the wavelength 337 used in this embodiment is used.
The absorption coefficient of nm light to polyimide resin is about 800
0 / cm.

The residual film thickness of the residual resin 22 on the printed circuit board 21 was measured using the inspection apparatus described in this embodiment, and it was confirmed that the residual polyimide thickness d was about 1 μm. In the above embodiment, the ultraviolet light 2 and the white light 38 are used. However, the present invention is not limited to this. For example, ultraviolet light having an absorption coefficient smaller than the absorption coefficient of the ultraviolet light 2 is used instead of the white light 38. You can also.

Further, in each of the above-described embodiments, the case where the copper foil 24 is used has been described. However, similar effects can be obtained as long as the reflectance of the aluminum foil or the like with respect to the laser beam is equal to or more than a predetermined value. The wavelengths of the ultraviolet light 2 and the excitation light 7 are
What is necessary is just to select suitably according to the material of the residual resin.

[0071]

Since the present invention is configured as described above, the following effects can be obtained. That is, a bottom portion of a concave portion formed by irradiating a laser beam to a laminated material formed by laminating a first material and a second material by a processing laser beam irradiation device to remove the first material. Since the illumination light irradiating device for irradiating illumination light to the residual material, which is the first material remaining without being removed, is provided, based on light from the residual material by irradiating illumination light to the residual material, It is possible to quickly and accurately know the status of the residual material without performing a visual inspection of light or a destructive inspection by measuring with a device.

Since the light detecting device for detecting the light from the residual material irradiated with the irradiation light is provided, the provision of the light detecting device makes it possible to mechanize the detection, and quickly and accurately without performing the destructive inspection. The status of the residual material can be known at a glance.

Further, since the illumination light irradiating device is configured to irradiate the excitation light for exciting the residual material to emit luminescence, the destructive inspection is carried out by visually observing the luminescence emitted by the residual material and measuring by the equipment. The situation of the residual material can be known without fail.

Further, the illumination light irradiating device is configured to irradiate excitation light for exciting the residual material to emit luminescence, and the light detecting device is configured to detect luminescence emitted from the residual material. Is detected, the status of the residual material can be known.

The illumination light irradiating device irradiates ultraviolet light having an absorption coefficient of a predetermined value or more with respect to the residual material, and the light detecting device detects the reflected light reflected from the bottom of the concave portion. So, using an ultraviolet light having an absorption coefficient equal to or greater than a predetermined value, the ultraviolet light is absorbed while passing through the residual material,
As the thickness and absorption coefficient of the residual material increase, the rate of reduction increases, so that the state of the residual material can be known with high sensitivity.

Further, an ultraviolet light irradiating device was used, and the absorption coefficient was 5
000 / cm or more UV light
By using ultraviolet light having an absorption coefficient of 5000 / cm or more, 0.6 μm compared to the case where the thickness of the residual material is 0.2 μm.
In the case of m, the intensity of the reflected light decreases by about 20%, that is, the brightness at the bottom changes by about 20%. If it changes to this extent, it can be easily detected by the reflected light detection device. If the film thickness of the residual material is about 0.2 μm, it can be removed by chemical treatment, so that no failure occurs. If it exceeds about 0.6 μm, it cannot be removed by chemical treatment, and it often becomes defective.
It is possible to easily detect a residual film thickness that causes a failure and prevent the failure.

Further, the illumination light irradiating device may be configured such that the first irradiation light whose absorption coefficient for the residual material is the first predetermined value and the second predetermined value whose absorption coefficient for the residual material is smaller than the first predetermined value. And irradiate the second irradiation light, and the light detection device detects the thickness of the residual material based on each reflected light of the first and second irradiation lights reflected from the bottom of the concave portion. Therefore, the absorption coefficients of the first and second irradiation lights with respect to the residual material are different, and those reflected on the surface of the residual material occupy a majority of the first reflected light, and are reflected on the surface of the second material. Since the reflected light occupies the majority of the second reflected light, the position of the surface of the residual material and the position of the surface of the second material can be detected from the first and second reflected light, and the difference between the positions of the two surfaces can be detected. Know the thickness of the residual material and take appropriate action if necessary. That.

Since the laser beam of the processing laser beam irradiation device is used as the illumination light irradiation device, the processing laser beam irradiation device can be used as the illumination light irradiation device, and the device is inexpensive.

Further, since the laser processing apparatus according to the present invention is provided with one of the above-described apparatus for inspecting the concave portion of each laminated material, the residual material can be immediately inspected without performing a destructive inspection after processing the concave section. The presence / absence can be known, and if necessary, processing for removing the residual material can be performed again, so that reliability and productivity can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a configuration of a laser processing apparatus including an inspection device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining the reflected light intensity when there is a residual resin in a concave portion in the inspection device of FIG. 1 and when there is no residual resin.

FIG. 3 is a configuration diagram of an inspection apparatus and a laser processing apparatus showing another embodiment of the present invention.

FIG. 4 is a configuration diagram of an inspection apparatus and a laser processing apparatus showing another embodiment of the present invention.

FIG. 5 is an explanatory diagram for explaining a state of reflection in the inspection device of FIG. 4;

FIG. 6 is a characteristic diagram showing a relationship between a residual film pressure of a residual material and a reflected light intensity in the inspection device of FIG.

FIG. 7 is an explanatory diagram for explaining the reflected light intensity when there is a residual resin in the concave portion in the inspection device of FIG. 4 and when there is no residual resin.

FIG. 8 is an explanatory diagram for explaining an operation of an inspection apparatus and a laser processing apparatus according to another embodiment of the present invention.

FIG. 9 is an explanatory diagram illustrating a light path when the focal position is shifted in the detection device of FIG. 8;

FIG. 10 is an explanatory view showing a conventional BVH processing method for a printed circuit board and illustrating a step of processing a fine through-hole portion.

FIG. 11 is a diagram illustrating a conventional BVH processing method for a printed circuit board, and is an explanatory diagram illustrating a processing method for processing a recessed portion forming a BVH.

FIG. 12 is a configuration diagram of a conventional laser processing apparatus provided with an optical microscope.

13 is a configuration diagram of the optical microscope in FIG.

FIG. 14 is an explanatory diagram for describing a state of reflection of irradiated light on a printed circuit board.

[Explanation of symbols]

1 light source, 2 ultraviolet light, 6 hole processing part, 6a bottom part, 7
Excitation light, 8 fluorescence, 11 CCD camera, 12 image processing device, 13 laser oscillator, 18 epoxy resin,
19 glass epoxy, 20 laser beam, 21 printed circuit board, 22 residual resin, 24 copper foil, 27 images,
29 resin surface reflected light, 30 copper foil surface reflected light, 32
a, 32b Reflected light from the bottom of the hole processing part, image of the 33 hole processing part, 38 white light, 39a, 39b pinhole plate.

Claims (9)

[Claims] 1. A recess formed by removing a first material by irradiating a laser beam to a laminated material formed by laminating a first material and a second material by a processing laser beam irradiation device. A concave material inspection device for a laminated material, comprising: an illumination light irradiating device that irradiates an illumination light to a residual material that is the first material remaining without being removed at a bottom of the portion. 2. A light detecting device for detecting light from a residual material irradiated with irradiation light.
3. The apparatus for inspecting a concave portion of a laminated material according to claim 1. 3. The inspection apparatus according to claim 1, wherein the illumination light irradiating device irradiates an excitation light for exciting the residual material to emit luminescence. 4. An illumination light irradiation device for irradiating excitation light for exciting residual material to emit luminescence, and a light detecting device for detecting luminescence emitted from the residual material. The apparatus for inspecting a concave portion of a laminated material according to claim 2. 5. An illumination light irradiating device for irradiating ultraviolet light having an absorption coefficient of a predetermined value or more with respect to a residual material, and a light detecting device for detecting reflected light reflected from the bottom of the concave portion. The apparatus for inspecting a concave portion of a laminated material according to claim 2, wherein: 6. An illumination light irradiating device having an absorption coefficient of 5000
6. The apparatus for inspecting a concave portion of a laminated material according to claim 5, wherein the apparatus is irradiated with an ultraviolet light of not less than / cm. 7. An illumination light irradiating device, wherein a first irradiation light whose absorption coefficient for a residual material is a first predetermined value and a second predetermined value whose absorption coefficient for said residual material is smaller than said first predetermined value. And irradiate the second irradiation light, and the light detection device detects the thickness of the residual material based on each reflected light of the first and second irradiation lights reflected from the bottom of the concave portion. 3. The apparatus for inspecting a concave portion of a laminated material according to claim 2, wherein the inspection is performed. 8. The recess of a laminated material according to claim 1, wherein a laser beam of a processing laser beam irradiation device is used as the illumination light irradiation device. Inspection equipment. 9. A laser processing apparatus provided with the apparatus for inspecting a concave portion of a laminated material according to claim 1. Description: